Bacteria, fungi, viruses, algae and other microorganisms are always present in our environment. Such microorganisms are an essential part of ecological systems, industrial processes, and healthy human and animal bodily functions, such as digestion. In other instances, however, the presence of microorganisms is highly undesirable because they can cause illnesses or death of humans and animals, create odors and damage or destroy a wide variety of materials.
The species and numbers of microorganisms present vary depending on the general environment, on the nutrients and the moisture available for the growth of the microorganisms, and on humidity and temperature of the local environment. Nutrients for microorganisms abound in the normal environment. Any protein matter such as dried skin, discarded foods, plants, and animal wastes all are excellent nutrient media for many types of potentially harmful microorganisms. Furthermore, many organic synthetic and natural materials like plastic coatings and objects, and wood, paper and natural fibers can serve as nutrients for microorganisms that will degrade the materials. In addition, certain bacteria are capable of remaining viable in a dormant state on floors or on objects for long periods of time until they are deposited in the proper media for growth. Consequently, potentially harmful microorganisms can be transported by routine traffic on floors, or by the act of brushing against walls or furniture or by handling objects.
Air filtration devices in air handling systems normally serve two purposes: to protect sensitive mechanical equipment from dirt and debris, and also to remove potentially health-hazardous particulates from the air. Particulates that build up on air filtration devices can include a variety of components, such as chemical and detrital dusts, pollen, bacteria and mold spores, insects, bits of plant matter, skin scales, fibers and other materials, depending on environmental conditions. As the filter begins to accumulate a particulate layer, the ability for moisture retention on the surface of the filter increases. As moisture is retained in the particulate layer, conditions become favorable for bacteria and mold spores to germinate and grow. This microbial proliferation results in the production of even higher concentrations of new spores, some of which may be formed in hyphae that have penetrated through the filter on the downstream side. These spores can cause hypersensitivity responses (coughing, sneezing, teary eyes and upper respiratory ailments in humans), and in some cases, even invasive infections of immunocompromised individuals.
Fiberglass insulation and rigid fiberglass duct board have become critical components of virtually all heating, ventilating, and air conditioning (HVAC) systems in the past twenty years. HVAC systems play valuable roles in energy conservation, and impart sound dampening characteristics to the system. Recent concerns over indoor air quality and microbiological contamination have spurred investigations into the role that HVAC components and surfaces play in harboring deleterious bacteria and fungi. These investigations have shown that the "porous, mat-like" physical characteristics of fiberglass insulation and rigid fiberglass duct board make it susceptible to moisture absorption and particulate accumulation as air circulates around or through it.
Prevention of spore germination and microbial survival during particulate build-up on air filtration devices and HVACs would have obvious benefits. Treatment of filters to inactivate microorganisms would not only help to reduce the risk of hypersensitivity reactions, but would increase the useful life of the devices. Many air filters are prepared from natural materials, such as cellulose, that are rapidly degraded under moist conditions by certain fungi. The fiberglass used in HVAC insulation is not a food source for microorganisms, however, many cellulose facing materials and fiber binding lattices have been shown to be degraded rapidly under moist conditions by certain fungi.
Filter life is also extended when antimicrobial activity is present, because biomass increase on and in the filter can clog pores, lessen air flow, and increase back pressure on the blower system. Reduction of viable biomass on the surface of insulation materials and duct board would help the HVAC system operate more efficiently by keeping the walls of the duct free of obstructive microbial growth.
It is well recognized that a major difficulty in health care facilities, such as hospitals and nursing homes, is the spread of dangerous infectious diseases caused by a wide variety of microorganisms. The problem is exacerbated in these facilities because many of the patients are in a weakened condition due to their primary health care problem. A microorganism that would not be a major threat to a healthy person could be fatal to a patient with a diminished capacity to defend himself from infection.
Potentially dangerous microorganisms are spread in health care facilities and elsewhere by a variety of vectors. One of the most common vectors is health care personnel. For example, a nurse or doctor may administer care to one patient and then be called upon to treat a second patient. Even though he or she may carefully wash his or her hands before treating the second patient, potentially dangerous microorganisms may be transferred from the first patient to the second patient. The microorganism can then cause a serious infection in the second patient.
Furthermore, plastic products are often used in hospitals and other health care facilities. These products are particularly susceptible to contamination by bacteria and other harmful organisms. Conventionally, the plastic products in these facilities are periodically cleaned with strong cleansers to remove or kill accumulated microorganisms. Between these cleanings, however, it is possible for the plastic products to accumulate a sufficient quantity or quality of bacteria or other microorganisms to constitute a major vector for cross-infection or spread of infectious diseases.
Pathogenic microorganisms can also be deposited on fabrics such as towels, clothes, laboratory coats and other fabrics. These microorganisms can remain viable on these fabrics for long periods of time. If the fabrics are used by several different people, the microorganisms can be transferred by people walking from one part of the facility to another.
As mentioned above, the plastics that are used to make plastic objects and coatings can themselves be a substrate for growth of various microorganisms, such as bacteria, mold and mildew. The same is true for fibers and fabrics, some of which are plastics and other organic materials such as wood and paper. When these microorganisms grow on or in a plastic product, fiber, or fabric, they form unsightly colonies. In addition, such microorganisms can eventually break down a plastic, fiber, fabric, or other material. Plastic, fiber and fabric products often must therefore be frequently cleaned with a strong cleanser to destroy, or at least control, the growth of the microorganisms. A more effective approach to the problem is clearly needed.
Potentially destructive microorganisms also tend to collect and reside in clothing and in fabrics regardless of whether they provide a nutrient substrate. Clothing that is used when exercising is particularly susceptible to the accumulation of destructive microorganisms. If these microorganisms are not killed or inhibited, they can cause extensive damage to the fabric, not to mention causing offensive odors and infections. Washing with conventional detergents does not always kill or remove many of these microorganisms. Thus, a microbiocidal additive is needed that will kill or inhibit the microorganisms residing on the fabric and, at the same time, not cause deterioration of the fabric and not cause adverse physical reactions in the individual that is wearing the fabric.
It is evident that the control of microbial contamination and infection has been a major problem in both industry and the home, and that the resulting infection and contamination continues to cause disease, death, and destruction of property. It has proved difficult, however, to develop a microbiocidal additive that is effective in controlling the growth of a wide variety of unwanted microorganisms and is, at the same time, safe for use around human beings and animals. Accordingly, there is an acute need, both in industry and in the home, for a safe and effective microbiocidal additive that can be used in or on a wide variety of substances to impart microbiocidal activity to the product from which the substance is made.
One of the sources of difficulty in the control of potentially harmful microorganisms is the extreme variability of response of various microorganisms to conventional microbiocidal agents. For example, bacteria, which are classified as procaryotes, can be killed or inhibited by many different types of antibiotics. However, these same antibiotics that are effective against procaryotic organisms are usually ineffective against eucaryotic microorganisms, such as fungi and yeasts.
Even within the family of Bacteriaceae, there are two broad categories of bacteria known as Gram-positive and Gram-negative bacteria. These classifications are based on the ability of bacteria to absorb certain vital stains. The two groups of bacteria generally respond differently to the same microbiocidal agent. A particular agent that may be effective against one group may not be effective against the other bacterial group.
One conventional method of inhibiting the growth of both eucaryotes and procaryotes or both Gram-negative and Gram-positive bacteria is to combine two or more microbiocidal inhibitors, each designed to inhibit or kill a specific organism or class of organisms. However, various problems arise when introducing two or more additives into a material such as a detergent. The multiple additive system may alter the physical properties of the detergent into which it is mixed. In addition, the multiple components must be tested to insure compatibility and continued microbiocidal effectiveness when combined with the detergent. The relative microbiocidal or microbiostatic strength of each of the components in the multiple system must be determined. It is not uncommon for the combination of microbiocidal additives to initially have effective inhibiting or killing properties for both Gram-positive and Gram-negative organisms whereupon, with the passage of time, one or the other of the inhibiting additives will deteriorate and lose its effectiveness while the other inhibiting additive remains effective. In addition, one additive may have an unexpected inhibitory effect on the other additive. In addition, the requirement of adding two or more additives can become prohibitively expensive.
The ideal microbiocidal additive should be relatively nontoxic to humans and animals in contact with the additive. Such an additive should not cause an allergic reaction and must have no long term detrimental health effects on humans or animals. A microbiocidal additive should be compatible with the material with which it is being used and not cause the material to deteriorate or lose its desired properties.
It would also be of value to provide a microbiocidal agent that imparts other valuable properties to the material to which it is applied, for example, reduction of electrical resistance.
Accordingly, it is an object of the present invention to provide microbiocidal compositions and materials treated with microbiocidal compositions that kill or inhibit the growth of microorganisms.
It is another object of the present invention to provide air filtration systems that incorporate broad spectrum microbiocidal agents.